Github App access token unable to open PR

[marmoure]

We have created a GitHub App, one of its functions is to (on behalf of a GitHub user) fork an (upstream) repository on their behalf, create a branch, make some commits to the branch, and then send a PR from their fork back to the upstream repository.

For our App we have followed the "Authenticate as an app installation" method (see: https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/about-authentication-with-a-github-app) as we want to "attribute app activity to the app".

Unfortunately when our App tries to open the PR against the upstream repository we are getting the following error response from the GitHub API: "resource not accessible by integration".

It seems that other apps such as Depenadabot (see: https://github.com/apps/dependabot) are capable of doing this, for example where it opened this PR: evolvedbinary/exist#27.

Below is a code snippet where we are using JavaScript and the GitHub provided Octokit library (see: https://github.com/octokit) to try and achieve this.

What are we doing wrong?

    // get the access token for the installation
    const installationId = 0; // Your installation ID

    // Authenticate as the GitHub App using the JWT
    const jwttoken = ``

    const octokitApp = new Octokit({
      auth: jwttoken,
    });

    const response = await octokitApp.request('POST /app/installations/{installation_id}/access_tokens', {
      installation_id: installationId, // Your installation ID
    });

    const accessToken = response.data.token;

    const octokit = new Octokit({
      auth: accessToken
    });

    const response = await octokit.pulls.create({
      owner: 'evolvedbinary',
      repo: 'prosemirror-lwdita',
      title: 'Update README.md',
      body: `This pull request was created by **Petal-demo bot**`,
      head: 'marmoure:patch-1',
      base: 'main',
    });